docs: def _is_finished(self, as_of):
          """Have the specified number of billing cycles been completed?
  
          If so, we should not be enacting this RecurringCost.
          """
          if self.is_one_off():
              last_billing_cycle = self.get_billing_cycles()[self.total_billing_cycles - 1]
              return last_billing_cycle.date_range.upper <= as_of
          else:
              return False